Field Study of Water Quality within the Toppenish Creek Restoration Site

Toppenish Creek is a perennial stream located in the lower Yakima Valley in the south-central region of Washington State and within the Yakama Indian Reservation.  The Bonneville Power Administration (under the Northwest Power Act) agreed to fund the Yakama Indian Nation’s Lower Yakima Valley Wetlands and Riparian Project.  Implementation of the project began in 1992 and was designed to protect, restore and manage floodplain lands along anadromous fish-bearing waterways on the Yakama Reservation.  In order to reestablish the Toppenish Creek wildlife habitat, the hydrology of the Toppenish Creek Watershed was restored.   Channels were reconnected along Toppenish Creek allowing the floodplain to flood again.  Hydrologic reconnection allowed for natural reintroduction of native wetland and riparian plants. 

The goal of this project was to determine whether the Toppenish Creek wetlands are a nutrient “sink” or “source” (pertaining to nitrates and phosphorous) and whether the amounts of these nutrients remain constant or change throughout the growing season.  To achieve this goal we obtained permission from the Yakama Indian Nation to enter the Toppenish Creek Restoration areas, identified sampling sites along the stream, collected weekly water samples, and measured flow to calculate discharges.  Water samples were analyzed for nutrient concentrations (nitrogen and phosphorus) and bacteria counts.  Using this data, we anticipated to develop a mass balance model of the Toppenish Creek.